Methods of constructing sheathed electric heaters



Nov. 18, 1958 J. VAN IN1-HOUDT 2,861,162.

METHODS 0F' CONSTRUCTING SIIEATI-EIDl ELECTRIC HEATERS Original-.FilledJune 23, 1951 s 1 Sax l /l' United States Patent METHODS OF CONSTRUCTINGSHEATHED ELECTRIC HEATERS John Van Inthoudt, Milwaukee, Wis.

Continuation of application Serial No. 233,196, June 23, 515.78 Thisapplication May 17, 1956, Serial No.

5 Claims. (Cl. 201-67) This invention relates to methods of constructingsheathed electric heaters. This is a continuation of my applicationSerial No. 233,196, now abandoned, tiled June 23, 1951.

A primary object of the invention is to provide improved forms ofnon-breakable, moisture impervious end seals for heaters of theaforementioned type.

Another object is to provide simplified methods of s sealing the ends ofsuch heaters.

A more specilic object is to provide a method of assembly wherebyclosure means affording permanent sheath end seals also serve to closethe sheath ends during assembly, thus eliminating the need for temporaryclosure devices during assembly, and

Another specific object is to effect permanent sealing of the sheathends as an in'cident to contraction of the sheath during swaging of thelatter for compaction of the insulating ll.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments of theinvention which will now be described, it being understood that suchembodiments are susceptible of modification in respect of detailswithout departing from the scope of the appended claims. Y

In the drawings: Y

Figure l is a view in longitudinal section of a portion of a tubularsheath heater following insertion' of the heating element therein butprior to the insertion of an end plug therein;

Fig 2 is like Fig. l but shows the heater at a later stage in itsconstruction;

Fig. 3 is like Fig.' l, but shows the heater at a still later stage inits construction; Y

Fig. 4 is like Fig. 3 but shows a modified form of en'd seal, and v Fig.5 is like Fig. 3 but shows still another modied form of end seal.

One preferred method of assembly of a tubular sheathed electric heaterinitially comprises threading through the bore of atubular sheath 10, aheating element, having a helical resistor 11 and end terminal members12, so that one such terminal member extends in part beyond the end ofthe sheath as shown in Fig. 1. Then a silicone rubber plug 13 of elasticcharacter, in its normal incompressed state, and having a centrallongitudinal perforation 13a is slipped over such terminal member andinserted into the end of the sheath. As shown in Fig. 1, the sheathpreferably has its bore enlarged adjacent the ends thereof to provideend recesses 10e, and the plug 13 is adapted to seat against the innersheath wall surrounding a recess 10et when inserted therein. The lengthof the plug 13 is preferably somewhat in excess of the l depth of therecess 10a, and such plug is preferably externally formed to match thecross sectional form of such recess, but with slightly greaterdimensions so that it will initially seat in bottle stopper fashion.With the plug 13 so seated, the portion of the sheath adjacent said iceplug is swaged to a limited degree (Fig. 2) to insure that said plugwill lirmly grip the portion of a terminal, 12 projecting therethroughand provide for anchoring of the latter against displacement axially ofthe sheath bore during the subsequent filling operations. When tubularsheaths with enlarged end portions are used, this auxiliary swagingoperation reduces one enlarged end, containing a plug 13, to the samedimensions as the center or main body portion of the sheath.

It may now be assumed that the thus far assembled unit is placed in oneof the well known types of loading machines which are adapted to effectfilling of the sheath with a suitable granular refractory insulatingmaterial, such as magnesium oxide. The assembly is positioned in theloading machine vertically with the end containing the plug 13lowermost. The upper terminalmember (not shown) of the heating elementis suitably positioned centrally of the bore of the sheath and extendsthe proper distance outwardly of the upper end of the sheath. Granularinsulating material is then introduced into the sheath bore, accompaniedby intermittent compacting of such material within the sheath in a wellknown manner. Sheath 10 is preferably lled with such compacted granularinsulating material to the bottom of the other, or upper, recess (notshown) in the other end of the sheath and then removed from the loadingmachine. A plug, like plug 13, is then slipped over the upper terminalmember and seated within the upper recess, like 10a, as aforedescribed.

The assembly is then subjected to well known swaging operations over itsentire length to effect further compaction' of insulating material 14and consequent further contraction of the sheath in cross section.During such swaging operations the aforementioned plugs preventdisplacement of the insulating material out of the ends of sheath itl.The end portions of the sheath surrounding the plugs are contracted tothe same cross sectional dimensions as the other portion of the sheath,and consequently the plugs are compressed in place laterally bycontraction of the sheath and are extended axially to some extent, asshown' in Fig. 2. As best shown in Fig. 3, such lateral compression andaxial extension of the plugs results in tightly fitting and intimateendwise. engagement of the plugs with the compacted insulating material14, with the portions of the terminal members 12 which they surround,an'd with the portions of the inner sheath wall surrounding the plugs.The plugs will be securely anchored within the ends of the sheathagainst withdrawal axially; and the same thus afford permanent end sealsfor the sheath of moisture impervious and non-breakable character.

Provision' of the enlarged recesses 10a, as shown in Fig. l, preparatoryto assembly is not necessary. Such recesses permit some latitude inrespect of the initial cross sectional dimensions of the silicone rubberplugs, while insuring following swaging and contraction of the sheaththat the desired sealing action by the plugs will be had.

If annealing of the sheath is required, then emplacement of the siliconerubber end plugs would be deferred until following annealing of thesheath. In such case temporary end plugs, preferably of the typedisclosed in the Charbonneau Patent No. 2,652.622, granted September 22,1953, would be used in the sheath ends during the filling, swaging andannealing steps, and then the silicone rubber plugs would thereafter beinserted into recessed ends of the sheath, laterally compressed andanchored in place.

Fig. 4 depicts a modified form of construction for end sealing of asheathed heater, employing a silicone rubber plug 15 having afrusto-conical tapered portion 15a extending beyond the sheath ends.Fig. 5 depicts another aeeinea modied form of construction for endsealing of a sheathed heater, employing silicone rubber plugs 16, whichare initially short in length and inserted wholly Within the sheath endsso that in iinal sealed state a recess is provided in the sheath ends,in which auxiliary sealing materials or devices may be inserted ifdesired.

Any of the assemblies shown in Figs. 3, 4 and 5 may have any desiredform of terminal device secured to their terminal members to facilitateconnection of electrical conductors therewith.

While not li-mited thereto, the sheath end seal construction and themethods of making the same aforedescribed have proved to be particularlyadvantageous for heaters used in defrost service of refrigerationequipment where high moisture conditions prevail.

I claim:

1. The method of making a sheathed electric heater wherein a resistorwith a terminal end portion is surrounded by a tubular metal sheathcontaining granular refractory insulation in which said resistor isembedded, cornprising inserting into an end of said sheath prior totilling the same with granular insulating material a plug formed ofelastic heat resistant material which is perforated to receive aterminal end portion of the resistor, then filling said sheath to apoint adjacent its other end with granular refractory insulatingmaterial, and then contracting said sheath laterally over its entirelength for compaction of said insulatingmaterial and for lateralcompression of said elastic plug to anchor the same against axialdisplacement and to effect permanent sealing thereof with the compactedinsulating material, with the peripheral surface o-f said terminal endportion, and with the inner Wall of said sheath.

2. The method of making a sheathed electric heater, which comprisesinserting a resistor with terminal end portions into a tubular metalsheath, then inserting into an end of said sheath a plug formed ofelastic heat resistant material, perforated to receive a terminal endportion of the resistor, then filling said sheath to a point adjacentits other end with granular insulating material, and

then contracting said sheath laterally over its entire length forcompaction of said insulating material and compressive anchoring of saidelastic plug against axial displacement and permanent sealing thereofwith the compacted insulating material, with the peripheral surface ofsaid terminal end portion of the resistor, and with the inner wall ofthe sheath.

3. The method of making a sheathed electric heater, which comprisesinserting a resistor with terminal end portions into a tubular metalsheath, then inserting into an end of said sheath a plug formed ofelastic heat resistant material, perforated to receive a terminal endportion of the resistor, then lling said sheath to a point adjacent itsother end with granular insulating material, then inserting another likeelastic heat resistant plug in the latter end of said sheath, and thencontracting said sheath laterally over its entire length for compactionof said insulating material and compressive anchoring of said elasticplugs against axial displacement and to effect permanent sealing thereofwith the compacted insulating material, with the peripheral surfaces ofthe terminal end portions of said resistor, and with the inner wall ofsaid sheath.

4. The method of making a sheathed electric heater, which comprisesinserting a resistor with termin-al end portions into a tubular metalsheath, then inserting into an end of said sheath a silicone rubber plugof elastic heat resistant character, perforated to receive a terminalend portion of the resistor, then filling said sheath to a pointadjacent its other end with granular insulating material, and theninserting another like elastic heat resistant silicone rubber plug inthe latter end of said sheath, and then contracting said sheathlaterally over its entire length for compaction of said insulatingmaterial and compressive anchoring of said elastic heat resistantsilicone rubber plugs against axial displacement and to effect sealingthereof with the compacted insulating material, with the peripheralsurface of said terminal end portion of the resistor, and with the innerWall of said sheath.

5. The method of sealing the end of a tubular metal sheathed heaterhaving a resistor with a terminal element projecting beyond the end ofthe sheath and compacted refractory insulating material in which saidresistor and said terminal element in' part are embedded in spacedrelation to the inner sheath wall, comprising inserting into the end ofthe metal sheath at a selected stage in the assembly of the heater anelastic heat resistant silicone rubber plug, perforated to receive saidterminal element, and after assembly contracting said metal sheath tolaterally compress said elastic heat resistant plug for permanentlyanchoring the latter against axial displacement and to effect sealingthereof with the peripheral surface of said terminal element and withthe inner peripheral surface of said metal sheath.

References Cited in the iile of this patent UNITED STATES PATENTS Re.23,679 Charbonneau et al July 7, 1953 1,157,916 Wentworth Oct. 26, 19151,298,609 Wentworth Mar. 25, 1919 1,359,400 Lightfoot Nov. 16, 19202,375,058 Wiegand May 1, 1942 2,448,756 Agens sept. 7, 1948 2,460,795Warrick Feb. 1, 1949 2,475,756 Peulet July 12, 1949 2,480,903Charbonneau Sept. 6, 1949 2,538,808 Swiss Ian. 23, 1951 2,617,001 HasleyNOV. 4, 1952 2,624,829 Dzaack Ian. 6, 1953 2,635,163 Temple Apr. 14,1953 2,652,622 Charbonneau June 7, 1953 2,659,795 Boggs Nov. 17, 1953FOREIGN PATENTS 546,150 Great Britain June 30, 1942 624,422 GreatBritain June 8, 1949 UNITED STATES PATENT OFFICE CERTIFICATE 0FCORRECTION Patent Noa 2,861,162 November 18, l958 John Van lnthoudt Itis hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected'below,

yIn the grant, lines l, 2 and 3, for l'John Van lnthoudt, of Milwaukee,Wisconsin,H read John Van lnthoudt, of Milwaukee, Wisconsin, assignor toCutler-Hammer, Inc., of Milwaukee, Wisconsin, a corporation ofDelaware,-m; line l2, for HJohn Van lnthoudt, his heirs" readCutlerldammer, Incu its successors in the heading to the printedspecification, line 4, for nJohn Van lnthoudt, Milwaukee, Wis,H readJohn Van lnthoudt, Milwaukee, Wis., assignor to Cutler-Hamer, Inc.,Milwaukee, Wiso a corporation of Delaware u; column 2, line '7, for "oneenlarged end," read n one enlarged end portion,

Signed and sealed this 31st day of March 1959,

(SEAL) Attest:

KARL H AXLNE i ROBERT C. wAIsoN Attestng Officer i Conmssioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No2,861,162 November 18, 1958 JOhn Van lnthoudt lt is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as cor-1 rected'belowel 1n thegrant, lines l, 2 and 3, for HJohn Van lnthoudt, of Milwaukee,Wisconsin,H read John Van lnthcudt, of Milwaukee, Wisconsin, assigner toCutler-Hammer, Inc., of Milwaukee, Wisconsin, a corporation oiDelawarefm; line l2, for "John Van lnthoudt, his heirsH readCutlerI-Iamner, lnco its successors in the heading to the printedspecification, line 1, for "John Van lnthoudt, Milwaukee, Wis,H readJohn Van lnthoudt, Milwaukee, Wis, assignor to Cutler-Hammer, lncuMilwaukee, Wis., a corporation of Delaware column 2, line 7, for noneenlarged end," read w one enlarged end portion,

Signed and sealed this 31st day of March 1959,

(SEAL) Attest:

KARL H., AXLINE ROBERT C. WATSON Attesting Officer Conmssioner ofPatents

